The present invention relates to a circuit configuration for controlling a hydraulic brake system with anti-lock control and/or traction slip control. Pressure fluid is discharged from the wheel brake into a pressure-compensating reservoir for pressure reduction during a control action. Pressure fluid is introduced and/or returned into the brake circuit by activating or connecting an auxiliary-pressure source.
Auxiliary enengy is required for anti-lock or traction slip control performed by a brake system which is supplied for example by an auxiliary-pressure supply system. For this purpose, known brake systems of this type are equipped, for example, with a hydraulic pump which is run constantly or which is not switched on until commencement of the control operation. Some brake systems have an additional pressure-fluid accumulator, the condition of charge of which dictates the switching-on and off of the hydraulic pump.
The auxiliary energy, that is the auxiliary pressure, primarily is necessary in such controlled brake systems in order to compensate for the energy that is released in the phase of pressure reduction. The pressure fluid removed from the wheel brake and discharged into the pressure-compensating reservoir is pumped back into the brake circuit by means of the pump or is replaced by pressure fluid out of the accumulator.
The magnitude of pressure-fluid consumption widely varies depending upon the brake system and the mode of control. Frequent strong braking pressure variations with rapid braking pressure reduction and re-increase result in excessive auxiliary-energy consumption and are perceived by the driver as being unpleasant. Therefore, attempts have been made to control the pressure reduction and re-increase, to the extent possible, in such a fashion that the pressure amplitudes are low and the pressure in the wheel brake is maintained to the optimal braking pressure. This then provides a more comfortable pedal feeling. The amount of the auxiliary energy that is required in the worst case will adversely effect the manufacturing costs of the system, in particular, the size of the hydraulic pump, the (electric) drive motor of the pump and, in some cases, the hydraulic accumulator.
Therefore, it is an object of the instant invention to provide a circuit configuration for controlling an auxiliary-energy supply system which results in minimum auxiliary-energy consumption and which controls the pressure-variation amplitudes during a control action to a comparatively small value.